1. Field of the Invention
This present invention relates to mechanized lube applicators. More specifically, embodiments of the present invention are directed to a lube applicator for applying lubrication to the plungers of die cast machines.
2. Related Art
Die casting is generally performed by the use of casting molds attached to two separate plates, a stationary plate and a movable plate. The molds are "cast" by bringing the movable plate against the stationary plate ("closed position") so that the casting molds can act as a template for the desired casting. While the casting molds are in the closed position, melted material is injected into the casting mold through an injection sleeve by means of a plunger in fluid communication with the casting mold on the stationary plate. Once the fluid cools into a solid, the movable plate separates from the stationary plate to release the finished casting. This aspect of die casting is well known.
However, a constant problem experienced during die casting has been the wear and tear of the plunger during the die cast process. Early efforts to reduce wear and tear on the plunger was the use of grease within the plunger to reduce the friction experienced by the plunger as the plunger moved along the injection sleeve. However, grease caused numerous problems. Besides the messiness involved with the use of grease, grease was difficult to apply and was not uniformly effective throughout the entire injection sleeve. In addition, grease tended to adversely mix with the liquid casting material as the casting material passed through the injection sleeve.
In the past three or four years, the use of dry graphite lubricant for the die cast plunger has gained popular acceptance. However, existing applicators for dry graphite have failed to work effectively for extended periods of time. A constant problem has been the hardening of the dry graphite at the opening of dry graphite container, otherwise known as the hopper. Since the dry graphite is constantly exposed to air in the prior art devices, the natural moisture found in the air mixes with the dry graphite to clog the hopper. Given that prior art devices relied on gravity to pass the dry graphite to the dispensing sleeve of the lube applicator, the lube applicator would fail to dispense dry graphite, or constantly dispense uneven amounts of dry graphite on each trial. Therefore, the lube applicator would constantly have to be disassembled and cleaned after only a few uses for the lube applicator to work effectively. The cleaning process would greatly slow down the die casting process resulting in loss of time and labor costs. Alternative devices attempted to use a vacuum feed within the dispensing sleeve to prevent the clogging problem, but the vacuum feeders have also failed to provide satisfactory results. The additional intakes and outlets in vacuum feeders created clogging problems at additional locations.
An additional problem with vacuum feeders, as well as the push piston feeders, was that the amount of dry graphite used on each trial was not exact. There was no measuring means to ensure that either too little graphite or too much graphite was not used. Instead, whatever amount that fell by gravity into the dispensing sleeve of lube applicator was either vacuumed or pushed by the push piston into the injection sleeve.
Another problem with existing applicators has also been the fact that there is no mechanism to self-clean the inside of the injection sleeve. There are often instances where the dry graphite will collect in the injection sleeve causing too much dry graphite to accumulate near the opening where the liquid die cast material is released into the injection sleeve. However, prior applicators had no mechanism to remedy this problem. The only means was to manually clean the inside of the injection sleeve with a clean rag, but again this process would entail stopping the entire process to clean the injection sleeve.